Abstract: Please visit the following link for more details:http://cmb.physics.wisc.edu/journal/index.html
Please feel free to bring your lunch!
If you have questions or comments about this journal club, would like to propose a topic or volunteer to introduce a paper, please email Le Zhang (lzhang263@wisc.edu)

Abstract: Catastrophe theory is a method for describing the evolution of forms in nature. It was discovered by RenA`e Thom in the 1960aEuroTMs. Thom expounded the philosophy behind the theory in his 1972 book Structural stability and morphogenesis. Catastrophe theory is particularly applicable where gradually changing forces produce sudden effects. The applications of catastrophe theory in classical physics (or more generally in any subject governed by a aEuro~minimization principleaEuroTM) are noncontroversial and help us understand what diverse models have in common. The applications of the theory in the social and biological sciences have met with some resistance. (I donaEuroTMt know if any workers in these areas have been influenced by ThomaEuroTMs ideas.) In this talk I will discuss three examples: ZeemanaEuroTMs toy (the aEurooecatastrophe machineaEuro), light caustics, and ZeemanaEuroTMs explanation of stock market booms and busts.
The constantly evolving slides for this talk are available on my website.

Speaker: Sue Coppersmith, University of Wisconsin Department of Physics

Abstract: A series of weekly presentations and discussions of current research topics in physics by the scientists involved in those studies designed to expose students to the topics and excitement of the research frontier.

Abstract: The newly discovered Higgs-like particle may have modified interactions with the Standard Model particles. Naively, the strength of these interactions may be extracted from rate measurements at the LHC. However, Higgs decays into new light particles may dramatically affect the rates so that the extraction of the Higgs couplings is possible only under some theoretical assumptions. I will present a method for determining the Higgs couplings and total width based on the existing data and a well-motivated theoretical constraint.

Abstract: The most profound result of the spin-orbit interaction (SOI) on iridates is the Jeff=1/2 insulating state, a new quantum state that represents the novel physics in the 5d-based systems. The SOI vigorously competes with Coulomb interactions, non-cubic crystal electric field and Hund's rule coupling, and critically biases their mutual competition to stabilize ground states with exotic behavior, which sharply contrasts with traditional models. Indeed, two conspicuous phenomena are commonly observed among layered iridates: (1) the Jeff = 1/2 insulating state, and (2) relatively high magnetic ordering temperatures and complex magnetic states that are not predicted by existing models. In this talk, we review the underlying physical properties of the layered iridates, and report results of our study that emphasizes spin-orbit-tuned ground states stabilized by chemical doping, application of pressure and magnetic field; these weak perturbations are capable of directly reducing the SOI so as to rebalance comparable interactions to generate a rich phase diagram of strongly competing ground states controlled by the SOI.

Abstract: I will describe the emerging evidence for an epoch of significant growth of cluster galaxies at z ~ 1.5, about 10 billion years in the past. This evidence rules out the (overly) simplistic galaxy formation models that seem to fit the data at later times (ie. at z < 1). New measurements of rapid evolution in a number of critical probes of the growth of cluster galaxies aEuro" including a census of their stars, the colors of those stars, and the rates of star formation, mergers and black hole activity aEuro" all suggest the z ~ 1.5 era is a very active one in the formation and assembly of massive cluster galaxies.

Abstract: Neutrinos are the most elusive of the known fundamental particles. Nonetheless, over the last 15 years, heroic experimental efforts aimed at understanding neutrinos have discovered that neutrinos are more interesting than originally dictated by the standard model of particle physics. After introducing the neutrinos, I will discuss how we came to discover that they have tiny but nonzero masses, comment on the most recent observations, and try to explain why this is a big deal. I will then describe some of the fundamental questions related to neutrinos, and how we hope to answer some of them in the near future.